Fullerene, carbon nanotubes, graphene, graphite, and the like are low-dimensional nano-materials composed of carbon atoms. That is, carbon atoms arranged in a hexagonal shape may form zero-dimensional fullerene formed of a ball, may form carbon nanotubes one-dimensionally rolled, may form graphene of a two-dimensional monolayer, and may form graphite three-dimensionally stacked.
In particular, graphene has very stable and excellent electrical, mechanical, and chemical characteristics and is a very excellent conductive material in which electrons can move about 100 times faster than in silicon and current flows about 100 times more than in copper. This was demonstrated through experiments in 2004 when a method of separating graphene from graphite was found. Since then, a great deal of research on this matter has been carried out.
Graphene is subject to large-area synthesis on a wafer or a metal substrate. Thus, in order to apply the graphene to an electronic device, a process for transferring synthesized graphene onto an electrode substrate of the electronic device is needed.
Korean Patent Laid-open Publication No. 2010-0046633 describes a method for removing a carbonization catalyst from a graphene sheet formed on the carbonization catalyst by using a salt solution as an oxidizer that oxidizes the carbonization catalyst and transferring the removed graphene sheet onto a substrate or a predetermined position on a device.
Further, in order to transfer graphene onto a substrate, conventionally, a dry process, a wet process, a roll-to-roll process, and the like have been used. However, such processes are difficult to be used to actually mass produce graphene due to time inefficiency and high cost. In particular, if graphene is transferred onto a substrate by a roll-to-roll process, a rigid substrate such as a wafer, a glass, or the like substrate cannot resist pressure and friction during a transferring process, resulting in damage to the graphene.
Therefore, for industrial application of graphene, a method for transferring large-area graphene at low cost in a short time is highly demanded.